My invention covers apparatus for collecting (for purposes of subsequent analysis) a volatile composition of matter which is releasably bonded to a pliable porous substrate such as a towel, as well as a process for using such apparatus.
The properties of a pliable substrate (including physical, chemical and microbiological properties) affect the behavior of the substrate with respect to chemicals, particularly volatile chemicals, either naturally present in or on the substrate in a substance applied thereto and so affect the chemicals present in a headspace above the substrate. Conversely, the chemicals entrapped in the interstices of a porous substrate or on the surface of the porous substrate have an effect upon the properties of the substrate, for example, if the substrate is a towel and the towel contains a fragrance, the concentration of that fragrance and the nature of the fragrance in the particular substrate will affect the ultimate aroma in the headspace above the substrate after the substrate is utilized, washed and dried.
Considerably complicated techniques exist in the prior art for collection(for purposes of subsequent analysis) of volatile materials contained within a substrate. U.S. Pat. No. 5,891,729 discloses a method of characterizing a substrate which comprises applying a test formulation to said substrate, subsequently collecting volatile chemicals in a headspace above the substrate, determining a profile of the volatile chemicals so emanated and using said profile to characterize the substrate. Specific examples of substrates in U.S. Pat. No. 5,891,729 are skin, wood, hair, clothing, carpets, plastics, surfaces, ceramic tiles, wool, fabric or perfumed products.
Noting the complexity of the methods and techniques of U.S. Pat. No 5,891,729, it is apparent that a need exists for a more standardized and simplified technique for collection(for purposes of subsequent analysis) of a volatile composition of matter releasably bonded to a pliable porous substrate such as a towel.
Thus, for example, U.S. Pat. No. 5,891,835 issued on Apr. 6, 1999 discloses a cleaner impregnated towel comprising a flexible porous substrate and impregnated into the substrate a cleaner formulation comprising d-limonene, dibasic acid ester, N-methyl-2-pyrrolidone, secondary alcohol ethoxylate, sodium lauryl sulfate, polysorbate 80, a salt of a coconut oil, fatty acid ester of isethionic acid, glycerine, ethyl alcohol, an antimicrobial preservative and, optionally, water. Although the composition impregnated into the substrate is known initially, after the substrate is utilized, there is no teaching of a method for collecting (for purposes of subsequent analysis) the components impregnated into the substrate after initial use or after repeated use of the substrate, nor is there any teaching in U.S. Pat. Nos. 5,891,835 or 5,891,729 of apparatus or processes for a simplified technique for collecting (for purposes of subsequent analysis) the contents of such substrate.
My invention is directed to apparatus which will effect collection (for purposes of subsequent analysis) of compounds from the headspace over dry cloth as well as moist cloth and other substrates. The compounds are releasably bonded to the surface and/or in the interstices of the porous substrate.
More specifically, my invention is directed to apparatus and a process for collecting for purposes of subsequent analysis a volatile composition such as a perfumery composition located on the surface and/or in the interstices of a planar pliable porous substrate such as a towel section.
In practicing my invention, a planar surface of the substrate which contains the volatile composition is initially juxtaposed adjacent a solid wall (e.g., glass frit) porous to a nonreactive carrier gas such as air, nitrogen or carbon dioxide and fully and tightly covers the porous section of the wall. The carrier gas is passed through the porous section of the wall and then through the pliable porous substrate section which is adjacent the wall, after which the carrier gas will contain each component of the volatile composition. The composition-carrier gas mixture is then passed through a trapping substance (e.g., TENAX(copyright) [a polyphenylene oxide]) which entraps the molecules of each component of the volatile composition. The volatile composition can then be analyzed (e.g., using GLC, NMR and mass spectral techniques) after removing the trapping substance containing the entrapped components from the apparatus.
Thus, my invention is directed to apparatus for collecting for purposes of subsequent analysis a volatile substance such as a perfumery material releasably bonded to a substantially planar pliable porous substrate having an inner surface and an outer surface. The substrate is porous to the passage of a carrier gas therethrough in a direction substantially perpendicular to the inner and outer surfaces of the planar pliable porous substrate. The apparatus consists essentially of:
(a) hollow enclosure means (which can be cylindrically shaped or elliptical-cylindrically shaped) consisting of:
i. hollow outer enclosure means circumventing a first void space and consisting essentially of a base supporting a substantially cylindrical gas impermeable wall having exit port means therethrough;
ii. entirely surrounded by said hollow outer enclosure means, substantially cylindrically-shaped inner enclosure means situated within said first void space and circumventing a second void space, and having two spaced-apart oppositely situated end sections and a central section juxtaposed to and communicating with each of said oppositely-situated end sections, said central section being substantially parallel to the wall of said outer enclosure means, said central section having an outer surface and an inner surface, and said central section consisting of a cylindrically-shaped gas-permeable hollow frit structure for both (A) supporting the pliable porous substrate whereby, when in use, said porous substrate fully covers said laminar gas-permeable central section in an all-encompassing manner and (B) enabling carrier gas to flow from within said inner enclosure means second void space to the void space located between the outer enclosure means and the inner enclosure means, in a direction substantially perpendicular to and through said porous substrate, each of the two end sections being impervious to the flow of gas therethrough and one of the end sections having an entry port means communicating from without said hollow enclosure means to the second void space within said inner enclosure means;
(b) analyte collection means located downstream from said hollow enclosure means and communicating with the exit port means thereof, consisting essentially of tube trapping means whereby analyte mixture components emitted from said pliable porous substrate during gas flow therethrough are entrapped in said tube trapping means;
(c) upstream from said hollow enclosure means or down-stream from said analyte collection means, inert gas flow effecting means for effecting the flow of inert gas sequentially (I) through said entry port means; (II) through the porous pliable substrate means located on said hollow frit structure; (III) through said exit port means; and (IV) through said analyte collection means.
My invention is also directed to a process for collecting (for purposes of subsequent analysis a volatile substance (such as a fragrance composition or an insect-repelling composition) releasably bonded to a substantially planar pliable porous substrate (for example, a cloth or a towel fabricated from cotton or polyester) having an inner surface and an outer surface comprising the steps of:
(a) providing the apparatus as set forth, supra;
(b) providing said porous substrate;
(c) wrapping in an all-encompassing manner said porous substrate around said central section of said inner enclosure means of said apparatus whereby the inner surface of said porous substrate is removably adhered to and intimately adjacent to the entirety of the outer surface of the hollow frit structure of the inner enclosure means;
(d) effecting the flow of carrier gas sequentially (I) from a location upstream from the entry port means; (II) into the inner enclosure means through said entry port means; (III) through said hollow frit structure; (IV) through said porous substrate means in a direction substantially perpendicular thereto in substantially evenly distributed manner across the inner and outer surface thereof; (V) into and through the void space between the inner enclosure means and the outer enclosure means; (VI) through said exit port means of said hollow outer enclosure means; and (VII) into and through said analyte collection means,
whereby components of the analyte composition emitted from said porous substrate are trapped in said trapping means.
Preferably, the hollow enclosure means of the above-described apparatus contains two concentric cylindrical enclosures, with the outer cylindrical enclosure being impervious to gas except for an exit port and with the inner enclosure means having an entry port and having a centrally located solid porous surface (e.g., glass frit, or solid microporous polymer).
Preferably, after the pliable porous substrate is in place on the inner enclosure, carrier gas is forced through the inner enclosure past the porous substrate into the outer enclosure and then out of the outer enclosure into the analytical means which preferably contains a trapping material. The carrier gas, such as nitrogen, air or carbon dioxide, is inert and nonreactive with the porous substrate or with the volatile substance releasably bonded to the porous substrate. The carrier gas can either be forced through from a pressurized device upstream from the hollow enclosure means (e.g., a pressurized carbon dioxide cylinder), or the carrier gas can be pulled through using means downstream from the analytical apparatus means such as a vacuum pump.
Whether the inert gas flow effecting means is upstream from the remainder of the apparatus or downstream from the remainder of the apparatus, it is preferable to have a gas filter in place in the apparatus of my invention, upstream from the hollow enclosure means so that the inert gas is free of any contaminants which would interfere with the analysis of the composition releasably bonded to the substantially planar pliable porous substrate (e.g., towel section).
Preferably, the hollow outer enclosure means of the hollow enclosure means part of the apparatus of my invention is cylindrical and has a height dimension of from about 4 cm up to about 20 cm and a diameter dimension of from about 4 cm up to about 12 cm. Preferably, the inner enclosure means of the hollow enclosure means part of the apparatus of my invention is cylindrical and has a height dimension between from about 50% up to about 85% of the height dimension of the hollow outer enclosure means and a diameter dimension of from about 40% up to about 70% of the diameter dimension of the hollow outer enclosure means.
The support means part of the inner enclosure means (that is, the central section of the inner enclosure means) is preferably cylindrical or substantially cylindrical in shape and as stated, supra, is preferably glass frit or microporous polymer. However, other suitable support means are useful in the practice of my invention, for example, the material which is marketed as cylindrical filter screens by the B. C. McDonald and Company of St. Louis, Mo. 63132 under the description of xe2x80x9cRonningen-Petter Woven Wire Screenxe2x80x9d; or Ronningen-Petter Woven Synthetic Screen (illustrated in FIG. 1E which is described in the Brief Description of the Drawings and in the Detailed Description of the Drawings sections, infra); or the Ronningen-Petter Perforated Screen. The Ronningen-Petter Screens are manufactured by the Dover Corporation/Ronningen-Petter Division, P.O. Box 188, Portage, Mich. 49081. The Ronningen-Petter Cylindrical Screens useful as support means in the practice of our invention are specifically described in literature published by Ronningen-Petter entitled xe2x80x9chow to select filter screens for the removal of trace contaminants in a closed liquid system.xe2x80x9d
Other support means useful in fabrication of the central section of the inner enclosure means of the apparatus of my invention are described in U.S. Pat. No. 5,762,797 issued on Jun. 9, 1998 entitled xe2x80x9cANTIMICROBIAL FILTER CARTRIDGE,xe2x80x9d the specification for which is incorporated by reference herein, and U.S. Pat. No. 5,868,933 issued on Feb. 9, 1999 entitled xe2x80x9cANTIMICROBIAL FILTER CARTRIDGExe2x80x9d, the specification for which is incorporated by reference herein.
With respect to the analyte collection means located downstream from the hollow enclosure means and communicating with the exit port means of the hollow outer enclosure means, the analyte collection means part of the apparatus of my invention as stated, supra, consists essentially of tube trapping means whereby volatile substance components emitted from the pliable porous substrate during gas flow therethrough are entrapped in the tube trapping means. The tube trapping means preferably consists of a tube having a length in the range of from about 2 cm up to about 4 cm and a diameter of from about 0.1 cm up to about 0.4 cm. Thus, various trapping materials are useful in the practice of my invention. As stated, supra, TENAX(copyright) (a polyphenylene oxide, as described infra)is a preferable material. Various forms of TENAX(copyright) are useful, for example, TENAX(copyright)-GC. TENAX(copyright) is a registered trademark of ENKA, N.V. of the Kingdom of the Netherlands (CAS Registration No. 2438-68-9). Other forms of TENAX(copyright) and methods of production of such forms of TENAX(copyright) are described in the following U.S. Letters Patents, the disclosures of which are incorporated by reference herein:
U.S. Pat. No. 3,400,100 issued on Sep. 30, 1968 (xe2x80x9cPROCESS FOR THE PREPARATION OF POLYPHENYLENE ETHERSxe2x80x9d);
U.S. Pat. No. 3,644,227 issued on Feb. 22, 1972 (xe2x80x9cSEPARATION OF POLY(2-6-DIMETHYL-1,4-PHENYLEOXIDExe2x80x9d) FROM ITS BLENDS WITH OTHER POLYMERS);
U.S. Pat. No. 3,703,564 issued on Nov. 21, 1972 (BIS-POLYPHENYLENEOXIDE]ESTER BLOCK COPOLYMERSxe2x80x9d);
U.S. Pat. No. 4,431,779 issued on Feb. 14, 1984 (POLYETHERAMIDE-POLYPHENYLENE ETHER BLENDSxe2x80x9d); and
U.S. Pat. No. 4801,645 issued on Jan. 31, 1989 (xe2x80x9cTHERMOPLASTIC RESIN COMPOSITIONxe2x80x9d).
TENAX(copyright)-GC is actually a polyphenyleneoxide defined according to the structure: 
wherein N is an integer of from about 100 up to about 150.
Other trapping materials useful in the practice of my invention are as follows:
Activated Carbon marketed by Aldrich Chemical Company of 1001 West Saint Paul Avenue, Milwaukee, Wis. 53233 (Catalog Nos. 16, 155-1; 29, 259-1; 24, 223-3; 24, 224-1; and 24, 227-6);
Activated Alumina marketed by Sigma Chemical Company of St. Louis, Mo. (Catalog Nos. A8753; A8878; A9003; A1522and A2272);
Silica Gels marketed by Sigma Chemical Company (for example, Catalog Nos. S4004; S6628; and H8506); and
CHROMOSORB(copyright) (registered trademark of the Johns-Manville Company of Manville, N.J.), such as CHROMOSORB(copyright) LC-2; CHROMOSORB(copyright) LC-3; AND CHROMOSORB(copyright) LC-7, marketed by Sigma Chemical Company under Catalog Nos. C 0641; C 0766; C 5517 and C 6269.
The analyte collection means useful in the practice of my invention may contain, in place of the TENAX(copyright) (polyphenylene oxide) trapping substance, solid phase microextraction materials (xe2x80x9cSPMExe2x80x9d materials) such as those described in Bulletin 869 published by SUPELCO, INC., Supelco Park, Bellefonte, Pa. 16823-0048. An SPME example useful in the practice of my invention is 100 xcexcm polydimethylsiloxane fiber, Catalog No. 5-7300 of Supelco, Inc. The Supelco, Inc. Bulletin 869 is incorporated by reference herein. An additional description of the SPME (solid phase microextraction) technique useful in conjunction with the practice of my invention is the paper, Elmore, et al, J. Agric. Food Chem., 1997, Volume 45, pages 2638-2641, entitled xe2x80x9cComparison of Dynamic Headspace Concentration or Tenax [TENAX(copyright)] with Solid Phase Microextractlon for the Analysis of Aroma Volatiles,xe2x80x9d incorporated by reference herein.
As stated, supra, the means for effecting the flow of inert gas sequentially (i) through the entry port means of the inner enclosure means; (ii) and through the porous pliable substrate means located on the support means of the apparatus of my invention can be located downstream from the analytical apparatus means. If that is the case, the inert gas flow effecting means is a negative pressure pump means, preferably a vacuum pump of the xe2x80x9clow flowxe2x80x9d variety, for example, xe2x80x9cLow Flowxe2x80x9d pumps marketed by the Ametek Company of Largo, Fla. 34643 (the xe2x80x9cAmetek Constant flow Samplerxe2x80x9d).
The flow rate of inert carrier gas past the porous pliable substrate is preferably at a rate in the range of from about 20 ml per minute up to about 200 ml per minute of carrier gas, e.g., nitrogen, air or carbon dioxide.
At the indicated rates of carrier gas flow, a range of molar rates of release of volatile composition will occur from the porous substrate, e.g., towel section, in accordance with the following algorithm:       Δ    ⁢          xe2x80x83        ⁢    n    =            n      1        ⁡          [                                                  V              1                                      V              2                                ⁢                      e                          -                                                                    2                    ⁢                                          C                      V                                                        zR                                ⁡                                  [                                                                                    T                        2                                            -                                              T                        1                                                                                                            T                        2                                            +                                              T                        1                                                                              ]                                                                    -        1            ]      
wherein
n1 is the carrier gas flow rate in gram moles per hour;
xcex94n is the molar flow rate in gram moles per hour) of release of volatile composition from the pliable porous substrate;
V1 is the volume of the inner enclosure;
T1 is the temperature of the void space of the inner enclosure in xc2x0K (degrees Kelvin);
V2 is the volume between the porous pliable substrate and the outer enclosure;
T2 is the temperature of the carrier gas and volatile composition released from the pliable porous substrate (that is, the temperature of volume V2) in xc2x0K;       R    ⁢          xe2x80x83        ⁢                  is the gas constant            ⁡              [                  0.08206          ⁢                      xe2x80x83                    ⁢                                                    liter                            -                              atm                                                                    gm mole                            -                              xc2x0                ⁢                K                                                    ]              ;
z is the compressibility factor of the carrier gas; and
Cv is the heat capacity of the carrier gas defined as             (                        ∂          E                          ∂          T                    )        V    ,
xe2x80x83wherein
E is the internal energy of the carrier gas during flow through the apparatus of my invention.